Question

Describe how you would make a precision shaft with dimensions of 12 mm diameter, 30 mm long from cemented carbide.

Answer 1

7211-11-36Q AID: 1825 | 31/07/2013

Carbides such as tungsten carbide and titanium carbide that are bonded with metals like nickel, chromium, cobalt, and molybdenum are called as cemented carbides.

The manufacture of cemented carbide precision shaft of the required dimension is carried out in the following steps:

• In the first step, the metal powders are converted into carbides by carburization. Carburization is the heat treatment technique in which the metal is heated in the presence of carbon liberating compounds, and the metal gets hardened by absorbing the liberated carbon.

• The carbide powder is then ball milled in ball rollers along with binder material, so that the carbide particles get coated with the binder material.

• The next step involves compaction of coated metal powder in the form of billets or parts of desired sizes in a compaction chamber hydrostatically. These compacted shapes are less brittle and loosely packed.

• The compacted parts are then machined to accurate sizes of desired shapes by the use of diamond tool bit.

• The compacted material is then sintered to form cemented carbides. Sintering is a technique of forming solids from metal powders by atomic diffusion. In this method, the powdered metal is heated at a temperature just below its melting point causing the material particles to diffuse into each other causing fusion of the particles to form one single solid shaft with the required dimensions.